The present invention relates to throttling valves such as rotary throttle plates employed in the air inlet of an internal combustion engine. In particular the invention relates to such engine air throttles which are operated by a servo motor rather than direct mechanical linkage to a driver operated accelerator pedal.
The evolution of engine throttle operation from carbureted engines to electrically operated fuel injected engines has resulted in the desirability of electrically controlling the vehicle throttle from the engine electronic computer in a xe2x80x9cdrive by-wirexe2x80x9d arrangement. Such arrangements are desirable for traction control purposes and improved control under cruise control operation.
Where it has been desired to operate an engine air throttle with a servo motor, it has been proposed to operate the throttle shaft directly with a torque motor mounted on the throttle body with the output of the motor connected to the throttle shaft. In such an arrangement, the torque motor operates against a return spring which biases the throttle to the closed position upon de-energization of the throttle actuator torque motor.
In engines operating with an air throttle and fuel injection as opposed to carburation, the absence of the vaporized fuel in the throttle passage has resulted in greater tendency to form ice from the reduced vapor pressure of the flow without the fuel as the dynamic pressure by the flow velocity through the throttle passage. This formation of ice has resulted in sticking or lodging of the throttle plate when the throttle plate is in the nearly closed or idle position during engine operation. The formation of the ice has provided sufficient lodgment such that the throttle servo motor was subsequently unable to move the throttle.
Therefore, the problem to be solved is to provide a way or means of breaking loose a throttle plate which has been lodged or stuck from ice formation in an electrically operated engine air throttle without the need to substantially increase the power and size of the throttle servo motor in order to have torque available to crack the throttle loose from the ice.
The present invention provides a motorized engine air inlet throttle assembly which solves the above-described problem by providing a lost motion connection between the servo motor rotor and a driving member on the throttle shaft. In the event of throttle plate lodgment due to ice formation, the servo motor rotor rotates through a limited rotation and acquires rotary momentum relative to the driving member on the throttle shaft and subsequently impacts the driving member imparting a momentum transfer pulse to the driving member which is transmitted to the throttle shaft and breaks loose the throttle plate from the ice, thereafter enabling normal throttle operation by the servo motor.
The throttle servo motor is preferably of the type having an external rotor to increase the mass of the rotor which enhances the momentum transfer to the throttle shaft driving member where lost motion rotation has occurred due to throttle stickage. In the preferred embodiment, the throttle shaft driving has an arcuate slot; and, the servo motor rotor has a projection thereon which impacts the edge of the slot to impart a momentum transfer pulse thereto and effect breaking loose of the throttle plate.